1. Field of the Invention
The invention relates to weight lifting, particularly to a device for allowing a range of weight training movements utilizing barbells and dumbbells to be completed even after the weightlifter has reached severe muscle fatigue.
2. Discussion of Prior Art
It is well known that increasing the stress on a muscle being trained leads to increased muscle growth. To maximize a particular muscle's development one must contract the muscles over its full range of movement until the muscle's concentric force is dissipated. At this point a training partner is necessary to assist the weightlifter in performing several more repetitions in order to increase stress on the muscle and hence facilitate enhanced growth. The repetitions of the movement that are assisted by the training partner are called "forced repetitions".
When the weightlifter is in a training cycle that requires forced repetitions, he or she will need a training partner throughout the total training session. A session may be two, three, or more hours in length. Thus the training partner must either be solely dedicated to assisting the weightlifter, or must be able to alternate between his or her personal training routine and assisting the weightlifter with forced repetitions.
For most weightlifters the problem has been in insuring that a training partner would be available for the weightlifter on a continual basis, thereby insuring maximum development in a shorter period of time.
Heretofore, the operational design of weightlifting assistance devices which have been conceived have not taken advantage of the use of both barbells and dumbbells. Barbells and dumbbells are commonly referred to as free weights because of their unrestricted movement. Experienced weightlifters prefer free weights because they allow the user to experience muscle contraction through a full range of motion that is natural to the individual. In addition the balancing of the free weight brings into play other collateral muscles that would not be involved if the weight were being guided by machine action. Using the full range of motion and employing collateral muscles allows the weightlifter to develop muscle mass at an accelerated rate. In many cases dumbbells are used in conjunction with barbells because they allow the user to employ a greater range of motion than do barbells.
Earlier assistance devices which do not employ free weights have been found in three patents.
U.S. Pat. No. 3,998,100, dated Dec. 21, 1976 to Robert F. Pizatella et al. details an "Exercise Process and Apparatus" machine that automatically varies its resistance such that a user can move a simulated weight faster than a predetermined minimum velocity.
U.S. Pat. No. 4,765,618, dated Aug. 23, 1988 to David A. Sidwell details an "Accessory for Weight Lifting Equipment" which is an add on device for conventional stack weight machines or an apparatus that guides the movement of a barbell. Sidwell does not accommodate unrestricted free weight movement of the weight being lifted and in addition requires that a switch be manually manipulated for assistance in lifting or lowering the weight. Such manual switch operation requires the weightlifter to shift his or her hand, leg, or foot position. This often causes a break in concentration which adversely effects the lifting effort.
An "Apparatus for Positive Muscle Training is detailed in U.S. Pat. No. 4,921,244, dated May 1, 1990 to Kurt Berroth. Berroth also details an apparatus that may be added to existing stack weight machines. The apparatus assists the user in lifting the weight if the speed of the machine's weight falls below a predetermined rate. Berroth's device ceases its assistance to the user if the speed of the machine's weight falls below a preset lower threshold. Therefore the machine ceases operation just when the free weight user needs assistance. Furthermore the machine does not include the ability to recognize the apex of the movement being performed, hence the machine does not know when to stop the upward movement of a free weight. These factors render it ineffective for free weight applications.
Assist devices for barbells have been discovered in four patents. U.S. Pat. No. 4,949,959, dated Aug. 2, 1990 to William E. Stevens details a "Barbell Assist Device" which lifts and lowers barbells by use of a foot kick plate operated motor; U.S. Pat. No. 4,998,721, dated Mar. 12, 1991 to Douglas H. Anders et al. details a "Weightlifter's Exercising Apparatus" which also raises a weight by kick plate operated motor and lowers the weight by disconnecting the barbell from the motor; and U.S. Pat. No. 5,190,510, dated Mar. 2, 1993 to John Goodger details a "Bench Press Apparatus" which raises and lowers a barbell with a knee activated switch.
Because of their cable architectures all three of these barbell based inventions will not adequately support dumbbell press movements. Correctly executed dumbbell presses require that the weights be brought together at the apex of the movement. The inventions of Anders and Stevens will act to keep dumbbells separated when giving assistance. The invention of Goodger uses a single point of attachment to the weight being lifted, and therefore will not adequately support the use of two dumbbells. In addition these three inventions have been optimized only for the barbell bench press. The manual operation of the motor switch would become awkward or even dangerous for a standing exercise such as the squat because any shift in balance to operate the switch could cause the weightlifter to topple over.
A fourth barbell device is detailed in U.S. Pat. No. 5,048,826, dated Sep. 17, 1991 to William C. Ryan, entitled "Safety Apparatus for Use With Barbell Assembly". In its stated form the device does not find the apex of the movement but rather pulls the weight back to the height at which it was initially at rest. The device detects and terminates an erratic descent of a weight or the total lack of ascent of a weight, as opposed to compensating for growing fatigue when the weightlifter is lifting the weight. These factors render the device unsuitable for barbell forced repetition applications. In addition the dual cable architecture makes it unsuitable for general dumbbell use, as explained in previous examples.